A torque measurement system typically includes a rotor device (rotor) and a stator device (stator). The rotor is generally configured to attach to a rotating system such as an engine turbine, gearbox, transmission, or other piece of rotating equipment. The rotor includes strain gages for sensing torque, rotor electronics (RTE) for performing signal processing operations, and an antenna for inductively receiving power from the stator and for communicating with the stator. The stator is typically stationary and external to the rotating system and includes a coupling module in close proximity to the antenna of the rotor for receiving a signal from the RTE. The coupling module is often times in the shape of a caliper and referred to as a caliper coupling module (CCM). The CCM transfers the signal received from the rotor to stator electronics (STE) that perform signal processing to extract the torque measurements in the signal. The stator may, for example, work in conjunction with a personal computer to process and present the data collected by the RTE. The stator can also transmit instructions to the RTE, provide power to the RTE through inductive coupling, and receive status information transmitted by the RTE.
The rotor and stator each include an inductive antenna for bi-directional communication. Initially, the antennas are manually tuned at the factory where the torque measurement system is assembled. This tuning ensures that the rotor receives an adequate signal from the stator, and vice versa. This initial tuning generally matches the resonant frequency of the RTE and the STE close to the telemetry frequency through the selection of electronic components, such as capacitors. Manufacturing variations in electronic components, ageing of electronic components, as wells as variations in operating conditions, and other variable factors, however, can cause the tuning of the antennas determined during the initial tuning to no longer be accurate once a system is assembled and installed at a customer location. After assembly, however, the rotor antenna and stator antenna are typically not easily tunable.